EP0782983A2

EP0782983A2 - Process of preparing 2,2'-(1-Methyl-1,2-Ethanediylidene) bis (Hydrazine carboximidamide)

Info

Publication number: EP0782983A2
Application number: EP97400361A
Authority: EP
Inventors: Richard Philion; Steven A. Elenbaas
Original assignee: Sanofi SA
Current assignee: Sanofi Aventis France
Priority date: 1996-05-30
Filing date: 1997-02-18
Publication date: 1997-07-09
Also published as: JP2000511181A; CA2252606A1; AU3008497A; NO985551L; US5693673A; BR9710170A; WO1997045110A1; NO985551D0

Abstract

The invention concerns a process for preparing 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] comprising the steps of :

a) reacting aminoguanidine hydrochloride with methylglyoxal aldehyde or methylglyoxal dimethyl acetal in an acidic aqueous reaction medium to produce 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide]; and
b) purifying the 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] by recrystallization from an acidic aqueous medium.

Description

Field of the Invention

The present invention relates to a process of preparing 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] having greatly reduced impurities therein useful in a method of treating cancer or advanced malignant diseases.

Reported Developments

The compound 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximid-amide] is known by several names, such as 1,1'[(methylethanediylidene)dinitrilo] diguamidine, pyruvaldehyde bis (amidinohydrazone), mitoguazone and methylglyoxal bis-guanylhydrazone, methyl GAG or MGBG, represented by the formula
MGBG and its salts have been disclosed in the prior art since the 1950s for use against various diseases as illustrated by the following patents and publications.
The antitumor activity of MGBG in leukemia-L1210- and adenocarcinoma-755-bearing rodents was first reported by Freelander et al, 18 Cancer Res. 360 (1958).
Japanese 51044643 discloses MGBG and its acid addition salts as effective agents against virus diseases of fishes to prevent and treat infections, pancreatic necrosis and hematopoietic necrosis.
Japanese 50029520 discloses MGBG and its salts for use against influenza virus.
U.S. Patent No. 4,201,788 discloses MGBG for the treatment of non-malignant proliferative skin diseases.
MGBG is known to inhibit S-adenosylmethionine decarboxylase (SAMD), which is a key enzyme in polyamine synthesis, leading to cellular polyamine depletion. However, investigations with MGBG revealed unacceptable levels of toxicity. The toxicological effects of MGBG observed, some of which are peculiar to certain animal species, include gastrointestinal toxicity, delayed and fatal hypoglycemia, hepatic and renal damage, bone marrow depression, diarrhea and phlebitis. These effects have also prevailed in human subjects undergoing MGBG treatment. Additionally, several toxic effects were demonstrated which are unique to man. These include esophagitis, ulcerative pharyngitis, laryngitis, stomatitis, genital mucosa swelling, conjunctivitis, mucositis, erythema, edema, desquamating dermatitis, and profound anorexia with associated weight loss. Patients who were administered MGBG on a daily schedule exhibited remission to acute leukemia only after a precarious struggle with the oftentimes life threatening side effects. In many patients, treatment had to be discontinued before any beneficial results could be noted.
Knight et al in Can. Treat. Rep., 63 1933-1937 (1979) found that the levels of toxicity were dose schedule related and could be controlled. U.S. Patent No. 4,520,031 addresses the issue of such dose schedule related control in order to reduce toxicity.
The dose schedule control, as described in the patent was based on the postulation that MGBG exerts an inhibitory action relative to polyamine biosynthesis. Physiologically achievable effects of MGBG may be related to the inhibition of the enzyme S-adenosyl methionine decarboxylase, which catalyses the synthesis of the polyamine, spermidine.
Spermidine is believed to play an important role in the initiation of DNA synthesis. Studies have shown that MGBG-mediated depression of DNA synthesis is associated with spermidine depletion and putrescine accumulation.
Another area in which polyamines are believed to play a major role is in RNA synthesis, especially that of transfer (t) RNA. The methylation of tRNA may be directly stimulated by polyamines, a finding of particular interest in light of the reports that neoplastic tissue differs from normal tissue with respect to the extent of methylated tRNA. Here, too, spermidine appears to play a critical role.
Polyamine accumulation appears to be a necessary requisite to DNA synthesis at an optimal rate, in both normal and neoplastic tissues. Thus, the toxicity of MGBG observed in tissues with rapid turnover (skin, G.I. mucosa and bone marrow) may be directly related to inhibition of polyamine biosynthesis and a subsequent depletion of RNA and DNA, the agents which ultimately regulate cell replication. There is, however, strong evidence that: (1) polyamines are excreted in excess in the majority of cancer patients; (2) polyamines, especially spermidine, are released from tumor cells during and after effective chemotherapy, with an initial peak in excretion and in serum levels and subsequent drop toward normal values; and (3) chemotherapy which produces only bone marrow (or other normal tissue) toxicity, and is without antitumor effectiveness, does not produce a significant increase in polyamine excretion. The latter observation would suggest either that cancer cells have much higher levels of polyamines than normal cells, even those with higher rates of DNA synthesis, or that therapy which is effective produces rather specific effects on polyamine synthesis in cancer cells. Thus, the depletion of spermidine is associated with the action of MGBG.
In studies conducted on men, toxicological effects observed clinically have been attributed to cumulative effects of repeated daily doses. This cumulation or accretion of toxicity is possibly explained by the unusually prolonged period required for urinary elimination of MGBG in man. Bioavailability studies in man with MGBG-C¹⁴ have shown that following a single intravenous infusion over a period of 20 minutes, the radioactivity rapidly disappeared from the plasma and that over an extended period of 3 weeks approximately 60 percent of the drug was excreted unchanged in the urine. These data suggest that MGBG accumulates in the tissues and is slowly leached from tissue deposits to accomplish elimination.
The patentee, after considerably large number of studies conducted with MGBG in the treatment of various tumors, concludes that a weekly schedule of administration is most effective in achieving a higher therapeutic index while reducing toxicity to an acceptable level. Accordingly, a dose range of from 250 mg/m² to 1000 mg/m² of MGBG administered at weekly intervals was established for the treatment of various tumors.
While the above-indicated dose range decreases toxicological side effects and affords treatments of various tumors, long term accumulation of MGBG is still a problem requiring further studies and/or treatment modifications.
Applicants have conducted extensive studies of MGBG with the object to further reduce toxic side effects thereof. In the course of their studies it was discovered that MGBG contains relatively large amounts of impurities which may contribute to the toxicological side effects of MGBG. Accordingly, great efforts were expended to identify and reduce the amount of impurities present in MGBG and its salts.
The process of preparing guanylhydrazones is described by Baiocchi et al., J. Med. Chem., 6, 431 (1963) and Oliverio, Denham, J. Pharm. Sci., 52, 202 (1963).
The process comprises reacting of an aminoguanidine salt with the corresponding carbonyl compound in an aqueous or aqueous-alcohol medium in the presence of a catalytic amount of acid.
The process uses commercially available aminoguanidine bicarbonate and is described as follows.

General Preparation of Guanylhydrazones

To a solution of 0.11 mole (15g) of aminoguanidine bicarbonate in 125 mL of water was added slowly to the desired acid (a few drops of amyl alcohol was added in order to prevent foaming) until the pH of the solution was less than 7. The solution was filtered from trace amounts of insoluble solids. The appropriate carbonyl compound was then added to the slightly acid filtrate at ca 60°C. The amount of carbonyl compound used was such that the ratio of aminoguanidine per carbonyl function was 1:1. If the carbonyl compound did not dissolve in the aqueous mixture, ethanol was added until the reaction mixture was homogeneous. The solution was then stirred at room temperature for 16 hours. If a precipitate was formed the solid product was isolated by filtration. Otherwise the reaction mixture was evaporated until a solid residue was obtained using methanol, ethanol and a combination of solvents.
Recovery of guanylhydrazones was low.
In addition of low yield we have found that the products contained relatively large amounts of impurities.

Experimental

We have developed methods for analysis of mitoguazone dihydrochloride using various systems to identify and quantify its impurities. One system of analysis included High Performance Liquid Chromatography. Considered in terms of determining chromatographic impurity levels, a high degree of specificity provides confidence that all the potential species of interest are detectable. Where these species, including process impurities and degradation products, are not available to inject directly onto the chromatographic system, specificity testing is usually conducted on stressed samples using one or more techniques which can usually be placed in one of two broad categories:

(a) Use of a specialized detection system to extract further information from the analyte peak.
(b) Some form of comparison between complementary separation techniques, the first being the system under validation and the second being a system which, by virtue of its differing selectivity, might be expected to resolve species co-eluting in the first instance.

Equipment and Chemicals

HPLC data were generated using various Kontron (Watford, Herts) and Waters (Watford, Herts) pump, autosampler, column oven and detector models. HPLC data were processed using Multichrom- V1.8-2 (LabSystems, Altringham, Cheshire). UV/visible absorption spectra were captured using an HP 1040 diode array detector (Hewlett Packard, Bracknell, Berks.). Light stressing (Xenon source, filtered through window glass) was performed in a Haraeus Suntest- (Alplas Technology, Oxford). HPLC grade acetonitrile was obtained from Rathburn chemicals (Walkerburn, Scotland), HPLC grade heptane sulphonic acid (sodium slat), and inorganic chemicals were obtained from BDH limited (Poole, Dorset). ACVA (4,4'-Azobis(4-cyanovaleric acid)), a radical initiator, exposure to which mimics oxidative stress, was obtained from Aldrich (Gillingham, Dorset). Mitoguazone dihydrochloride and purified water were obtained in-house.

Stress Sample Preparation

Samples of mitoguazone dihydrochloride (approximately 370 mg, equivalent to 250 mg base) were accurately weighed into 50 mL volumetric flasks and stressed according to the conditions given below. Stressing was continued for a maximum of 7 days or until 20 to 50% degradation had been achieved. After stressing, samples were neutralized, if necessary, and diluted to volume with purified water to give ^∼5mg(base)/mL solutions for TLC analysis. Aliquots of these solutions were diluted with purified water to give ^∼1 mg(base)/mL solutions for use in impurity determinations by HPLC. Finally, aliquots of these solutions were either diluted in HPLC mobile phase to give ^∼0.01 mg(base)/mL solutions for HPLC assay.
The stress conditions are obtained by subjecting a given sample to heat, acidic conditions, basic conditions, aqueous conditions, oxidative conditions or light.

Stress Conditions

Heat: Sample held at 80°C for 7 days. Acidic: 10 mL of 0.1 M hydrochloric acid was added to the sample and the solution held at 70°C for 7 days. Basic: 10 mL of 0.1M sodium hydroxide was added to the sample and the solution held at 70°C for 2 days.
Aqueous: 10 mL of purified water was added to the sample and the solution held at 70°C for 7 days. Oxidative: 10 mL of a 0.1M aqueous ACVA solution was added and the sample held at 40°C for 7 days. Light: Sample received an overall illumination of ^∼15,000 klx hours (with associated UV).
Assay by HPLC analysis : Samples were chromatographed isocratically on a 25 cm x 0.46 i.d. Hypersil BDS C8 5 µm columns (Anachem, Luton, Beds.) using a mobile phase consisting of 0.05M potassium dihydrogen orthophosphate buffer containing 1 g/L of heptane sulphonic acid (sodium salt) and adjusted to pH 3.0 with concentrated orthophosphoric acid (89% by volume) and acetonitrile (11% by volume). The flow rate was 2 mL/minute, the detector wavelength was 283 nm, the injection volume was 20 µL and column temperature was 40°C. Samples were quantified with respect to an accurately prepared external standard (nominally 0.01 mg(base)/mL.

HPLC method for measuring Impurity Method levels :

Chromatographic conditions were as for the assay except a detector wavelength of 210 nm was used. A second HPLC system was used with an aqueous to acetonitrile mobile phase ratio of 85% to 15% by volume, primarily to estimate specific process impurities. Impurities were quantified with respect to an accurately prepared external standard (nominally 0.005 mg(base)/mL).

TLC Method for measuring impurity levels :

20µL of each sample was spotted onto a silica gel TLC plate (Merck 60F₂₅₄). The plate was developed to a height of 10 cm in an acetone/ammonium hydroxide (SG 0.88)/water (90:5:5% by volume) mobile phase. Impurities were estimated against dilute mitoguazone dihydrochloride spots, both under short wavelength ultraviolet light (254 nm), and following treatment with a nitroprusside (sodium)-ferricyanide spray reagent.

Results

Triplicate samples representing 0, 80%, 100% and 120% of the nominal mitoguazone dihydrochloride concentration were analyzed by HPLC.

The samples were prepared as described above under the heading « stress sample preparation » using the mobile phase mentioned above for the assay by HPLC analysis under the heading « stress conditions ». Actually, the samples were made up close to the % concentration intended. Accordingly the exact concentration of the samples was measured. It was reported in table I below as « % nominal added ». The « Percent nominal recovered » denotes the product recovered after HPLC. The results obtained are given in Table I.

TABLE I

Recovery Data
	HPLC DATA *
Sample Identity	% nominal added	% nominal recovered
Blank 1	0	0
Blank 2	0	0
Blank 3	0	0
80% 1	81.1	81.0
80% 2	80.9	80.4
80% 3	83.6	83.3
100% 1	101.5	101.6
100% 2	103.6	103.5
100% 3	104.6	104.2
120% 1	122.3	121.3
120% 2	121.9	122.5
120% 3	119.0	118.8

HPLC* Assays. Least Squares Regression Analysis of the data gave an average accuracy of 99.8% (Coefficient of Correlation 0.99935).

Analysis of Stressed Samples

Stressed samples were assayed by HPLC whilst chromatographic impurity levels were determined by HPLC and TLC. The chromatographic data are summarized in Table II.

TABLE II

Chromatographic Assay and Impurity Data for Stressed Mitoguazone Dihydrochloride
Stress Condition	HPLC Assays (% w/w)	Impurities by HPLC (% w/w)	Impurities by TLC (% w/w)
Control	100.6, 99.9	1.3	< 0.7
Heat	100.1, 100.2	1.1	< 1.1
Acidic	87.6, 87.0	14.0	< 12.5
Basic	74.9, 75.4	27.9	< 25.3
Aqueous	69.4, 69.1	31.9	< 29.5
Oxidative	93.7, 94.5	6.5	< 5.8
Light	99.9, 99.2	1.4	< 0.7

Using HPLC, TLC and mass spectroscopy, impurities contained in the starting materials or formed during the process of making the final product were identified and quantified.
We have found that the diaminoguanidine related impurities account for more than 70% of the total MGBG-dihydrochloride impurity level.
The general reaction scheme for the production of the impurities and their chemical names follows.

wherein

D = [2-[(Aminoiminomethyl)hydrazono]propylidene]-carbonimidic dihydrazide.
E = [2-[(Aminoiminomethyl)hydrazono]-1-methylethylidene]-carbonimidic dihydrazide.
F = Bis[2-[(Aminoiminomethyl)hydrazono]-1-methylethylidene]-carbonimidic dihydrazide.
G = Bis[2-[(Aminoiminomethyl)hydrazono] propylidene]-carbonimidic dihydrazide.
H = [2-[(Aminoiminomethyl)hydrazono]-1-methylethylidene][2-[(aminoiminomethyl)hydrazono] propylidene]-carbonimidic dihydrazide.

In copending application D.N. 70493, Ser. No. 08/655,512 filed of even date with the present application, reaction parameters were studied and modified in order to reduce impurities in the final product. Said copending application discloses a process for the preparation of 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] comprising the steps of :

a) removing impurities from aminoguanidine bicarbonate (H₂N-C(=NH)-NH-NH₂, H₂CO₃) by suspending aminoguanidine bicarbonate in water and filtering the suspension;
b) reacting the filtered aminoguanidine bicarbonate with methylglyoxal dimethyl acetal in an aqueous reaction medium to produce 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide]; and
c) purifying the 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] by recrystallization from an acidic aqueous-isopropanol medium.

An essential step in the process is the removal of the impurities from the aminoguanidine bicarbonate starting material by suspending aminoguanidine bicarbonate in water and filtering out the impurities from the suspension.
We have now discovered that instead of using aminoguanidine bicarbonate as a starting material, aminoguanidine hydrochloride may be used to react with methylglyoxal dimethyl acetal in an aqueous reaction medium to produce 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine caroximidamide]. The process which includes a subsequent purification step provides a final product which is at least 99.5% pure.
Similar results are obtained starting from methylglyoxal aldehyde instead of methylglyoxal dimethyl acetal.
The invention thus relates to a process for preparing 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] comprising the steps of :

According to a preferred embodiment, the process of obtaining highly purified 2,2'-(1-methyl-1,2 ethanediylidene)bis[bydrazine carboximidamide] involves reacting aminoguanidine hydrochloride with methylglyoxal dimethyl acetal which comprises the steps of :

a) dissolving one part aminoguanidine hydrochloride in a mixture of about 0.5 to 3 parts, preferably in about 0.93 parts, of water and about 0 to 3 parts of a water miscible organic solvent, preferably about 0.75 parts of isopropyl alcohol;
b) adjusting the pH of the solution to about 0 to 5, preferably about 0 to 1 with concentrated hydrochloric acid;
c) adding to the solution about 0.25 to 1 parts of methylglyoxal aldehyde, preferably about 0.5 parts of methylglyoxal dimethyl acetal, at a temperature of about 0 to 50°C, preferably at 25 to 30°C;
d) stirring the reaction mixture for about 1 to 48 hours, preferably for about 1 to 16 hrs at ambient temperature;
e) adding about 0.5 to 20 parts of a water miscible organic solvent, preferably about 5 parts of isopropyl alcohol, to the reaction mixture to produce the solid 2,2'-(1-methyl-1,2 ethanediylidene)bis[hydrazine carboximidamide];
f) collecting the solid crude 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] by filtration and washing the same with 1 to 10 parts of an organic solvent, preferably with 1 to 2 parts of isopropyl alcohol; and
g) optionally drying the crude final product before purification preferably in a 45°C vacuum oven.

The purification process of the crude 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] comprises the steps of :

h) dissolving the crude compound in about 0.5 to 4 parts of deionized water, preferably in about 2 parts of water, preferably deionized water;
i) adding about 0.5 to 2 parts of a water miscible organic sovent, preferably about 1 part of isopropanol;
j) adjusting the pH of the solution to about 0 to 5, and preferably to 0 to 1 with concentrated hydrochloric acid;
k) stirring the solution for about 0.5 to 2 hours while adding 0.1 to 2 parts of water, preferably deionized water and maintaining the temperature of the solution at about 28-32°C;
l) optionally filtering the solution to remove insoluble impurities;
m) adding to the filtered solution about 0.5 to 10 parts of a water miscible organic solvent, preferably about 5 parts of isopropyl alcohol to precipitate the compound;
n) cooling the mixture to about 0 to 25°C, preferably to about 10°C;
o) collecting the solid product by filtration and washing the filtrate with 0.5 to 10 parts of an organic solvent, preferably with one part of isopropyl alcohol; and
p) drying the purified product.

As used herein the process of synthesizing and purifying 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] also relates to and includes synthesis and purification of its various forms including its hydrochloride monohydrate, dihydrate and hemihydrate forms.
In the process of synthesizing and purifying 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] we prefer to use isopropyl alochol. However, other water miscible organic solvents which may be used include methanol, ethenol, n-propyl alcohol, tetrahydrofuran, acetic acid, dimethyl formamide, acetonitrile and dimethyl sulfoxide or mixtures thereof.
Aminoguanidine hydrochloride, methylglyoxal aldehyde and methylglyoxal dimethyl acetal are available commercially, such as from Aldrich Chemical Co., and they can also be made by processes known in the art.
A representative example (Example 1) of synthesizing and purifying 2,2'-(1-methyl-1,2-ethanediylidine)bis[hydrazine carboximidamide] illustrates the invention.

Example 1

(A) Synthesis

60.0 grams of aminoguanidine hydrochloride was dissolved in 56 milliliters of deionized water and 36 grams of isopropyl alcohol. The pH of the solution was adjusted to about 0 to 1 by adding concentrated hydrochloric acid. 30.96 grams of methylglyoxal dimethylacetal was added over 1.5 to 3 hours while maintaining the reaction temperature between 25 and 30°C. The reaction mixtue was then stirred at ambient temperature for an additional 16 hours. 240 grams of isopropyl alcohol was added and the reaction mixture was cooled to 10°C. The crude product which formed during the reaction process was collected by filtration and was washed with 90 milliliters of isopropyl alcohol. The washed filtrate was then dried in a 45°C vacuum oven over night. The yield was 87% of the theoretical yield.

(B) Purification

79.3 grams of the crude product obtained in (A) was dissolved in 159 grams of deionized water at 35°C. 60.7 grams of isopropyl alcohol was added to the solution and the pH was adjusted to 0-1 by adding concentrated hydrochloric acid. The pH adjusted solution was stirred for 1 hour while maintaining its temperature at 28-32°C and adding 10 milliliters of deionized water. The mixture was filtered to remove impurities, such as mechanical dirt particles. 312 grams of isopropyl alcohol was then added to the solution to precipitate the product. The mixture containing the precipitated product was cooled to between 8-12°C and stirred for about 15 minutes. The purified product was then washed with 68 milliliters of isopropyl alcohol and dried in a 45°C vacuum oven.
The yield of the purified product was 67.5% of the theoretical yield.

Comparative example 1

(A) Synthesis

2,2'-(1-Methyl-1,2-ethanediylidene)bis[hydrazinecarboximidamide]

Aminoguanidine bicarbonate (Aldroch 98.5 %) was slurried in deionized water at 35-40° C for about 30 minutes, the suspension was filetred to remove diaminoguanidine and other impurities amounting to about 1% w/w 505 g, 3.8 mol of the filtered aminoguanidine bocarbonate was suspended in 200 g deionized water and 300 g (156 mL) isopropanol to give a heavy, but stirrable mixture. Concentrated HCl (376 g, 37.8 %) was cautiously added dropwise over a 1.5 hr period to prevent excessive foaming (Note 1). The mixture stirred readily after 5% of the HCl had been added. The reaction was endothermic and the temperature was maintained at between 19° C and 28° C. At the end of the addition a clear colorless solution was obtained (Note 2). It was warmed to 32° C and stirred for 20 minutes (Note 3). The methyl glyoxal dimethylacetal (212 g, 1.79 mol) (Fluka, 98%) was next added over 1.5 hours at a temperature of 30-35° C (Note 4). The suspension was stirred overnight at ambient temperature. The mext morning isopropanol (2.0 kg) was added over 15-20 minutes. The suspension was cooled to about 10° C and stirring was continued for 1.5 hours. The solids were collected by filtration and rinsed with 2 x 200 mL isopropanol. After drying overnight in a vacuum oven at 30-35° C, 463 g (47 %) of the crude MGBG was obtained.
TLC [acetone 90, water 5, NH₄OH 5]; HPLC (Estimated Total Impurities : ≈ 0.79 %), NMR: (DMSO-d₆).

(B) Purification

A suspension of crude MGBG (460 g) in 920 g deionized water was warmed to 40-50° C to give a clear pale yellow solution. The mixture was cooled to 30° C and 920 mg conc. HCl was added. A pH of 0-1 was measured with litmus paper. Isopropanol (350 g, 446 mL) was added rapidly and the mixture stirred for 1 hour at 28-32° C. The solutions were filtered to remove insoluble material. The filtrate was added to the reaction flask and acidified further with 0.5 g of conc. HCl. The isopropanol (1.84 kg) was added over 10-15 minutes to the vigorously stirred solution. The mixture was cooled to 8-12° C and stirred for an additional hour. The solids were collected and the cake was rinsed with 2 X 200 mL isopropanol. After drying in a vacuum oven at 30-40° C for 24 hours, the recovery was about 90 %. HPLC (Estimated Total Impurities = 0.65 %, NMR (DMSO-d₆); IR (KBr).

Comparison

Samples of purified 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] produced by: 1.) reacting aminoguanidine bicarbonate with methylglyoxal dimethyl acetal according to the procedure of comparative example 1 or 2.) reacting aminoguanidine hydrochloride with dimethylglyoxal dimethyl acetal according to the procedure of example 1 were analyzed by HPLC. Comparative results are shown in Table II and Table III.

TABLE II

Assay Results For Lots of Aminoguanidine Bicarbonate Used in Production of MGBG and Assay Results of MGBG Produced Therewith.
MGBG Lots Produced From Aminoguanidine Bicarbonate	Impurities (related to 1,3-diamino-guanidine) by HPLC % w/w	MGBG ETI by HPLC Area %
L-1	1.0	1.73
L-2	0.54	0.77
L-3	0.38	0.65
L-4	0.2	0.60
L-5	0.2	0.64
L-6	0.2	0.44

TABLE III

Assay Results For Lots of Aminoguanidine Hydrochloride Used in Production of MGBG and Assay Results of MGBG Produced Therewith
MGBG Lots Produced From Aminoguanidine Hydrochloride	Impurities (related to 1,3-diamino-guanidine) by HPLC % w/w	MGBG ETI by HPLC Area %
L-7	none detected	0.07
L-8	none detected	0.04
ETI : Estimated Total Impurities.

Aminoguanidine hydrochloride was found to contain lower levels of impurities than aminoguanidine bicarbonate and gave a superior quality MGBG. Purity of MGBG produced by the use of aminoguanidine hydrochloride and according to the present invention was found to be as high as 99.9%. Such highly pure MGBG is well-suited for pharmaceutical compositions for the treatment of cancer and other diseases.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

A process for preparing 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] comprising the steps of :
a) reacting aminoguanidine hydrochloride with methylglyoxal aldehyde or methylglyoxal dimethyl acetal in an acidic aqueous reaction medium to produce 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide]; and

b) purifying the 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] by recrystallization from an acidic aqueous medium.
Process according to claim 1 in which step a) involves the reaction of aminoguanidine hydrochloride with methylglyoxal dimethylacetal.
A process according to any of claims 1 and 2 comprising the steps of:
a) dissolving one part aminoguanidine hydrochloride in a mixture of about 0.5 to 3 parts of water and about 0 to 3 parts of a water miscible organic solvent;

b) adjusting the pH of said solution to about 0 to 5 with concentrated hydrochloric acid;

c) adding to the solution about 0.25 to 1 parts of methylglyoxal aldehyde or methylglyoxal dimethyl acetal at a temperature of about 0 to 50°C to obtain a reaction mixture;

d) stirring the reaction mixture for about 1 to 48 hours at ambient temperature;

e) adding to the reaction mixture about 0.5 to 20 parts of a water miscible organic solvent to produce the solid crude 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide];

f) collecting the crude 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine caroximidamide] by filtration and washing it with 1 to 10 parts of an organic solvent;

g) dissolving the obtained crude 2,2'-(1-methyl-1,2 ethanediylidene)bis[hydrazine carboximidamide] in about 0.5 to 4 parts of water;

h) adding to the solution about 0.5 to 2 parts of a water miscible organic solvent;

i) adjusting the pH of the solution to about 0 to 5;

j) stirring the solution for about 0.5 to 2 hours while adding about 0.1 to 2 parts of water and maintaining the temperature of the solution at about 28 to 32°C;

k) optionally filtering the resulting solution to remove insoluble impurities;

l) adding to the solution about 0.5 to 10 parts of a water miscible organic solvent to precipitate 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide];

m) cooling the mixture to about 0 to 25°C ;

n) collecting the solid 2,2'-(1-methyl-1,2,-ethanediylidene)bis[hydrazine carboximidamide] by filtration and washing it with 0.5 to 10 parts of an organic solvent; and

o) drying the purified 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide].
Process according to any of claims 1 to 3 in which the water miscible organic solvent is selected from methanol, ethanol, n-propyl alcohol, tetrahydrofuran, acetic acid, dimethylformamide, acetonitrile, dimethylsulfoxide and isopropyl alcohol.
Process according to any of claims 1 to 4 in which the water miscible organic solvent is isopropyl alcohol.
A process according to any of claims 1 to 5 comprising the steps of:
a) dissolving one part of aminoguanidine hydrochloride in a mixture of about 0.93 parts of water and about 0.75 parts of isopropyl alcohol;

b) adjusting the pH of the solution to about 0 to 1 with concentrated hydrochloric acid;

c) adding to the solution about 0.5 parts of methylglyoxal dimethyl acetal at a temperature of 25 to 30°C;

d) stirring the solution for about 1 to 16 hrs at ambient temperature;

e) adding about 5 parts of isopropyl alcohol to the reaction mixture to produce the solid 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide];

f) collecting the solid crude 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] by filtration and washing it with 1 to 2 parts of isopropyl alcohol;

g) dissolving the obtained crude 2,2'-(1-methyl-1,2-ethandiylidene)bis[hydrazine carboximidamide] in about 2 parts of water;

h) adding about one part of isopropyl alcohol;

i) adjusting the pH of the solution to 0 to 1 with concentrated hydrochloric acid;

j) stirring the solution for about 0.5 to 2 hours while adding 0.1 to 2 parts of water and maintaining the temperature of the solution at about 28-32°C;

k) filtering the solution to remove insoluble impurities therefrom;

l) adding to the filtered solution about 5 parts of isopropyl alcohol to precipitate the 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide];

m) cooling the mixture to about 10°C;

n) collecting the solid 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] by filtration and washing it with one part of isopropyl alcohol; and

o) drying the 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide].
2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] prepared by the process of any of claims 1 to 6.
2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] according to claim 7 having a purity of at least 99.9 %.
Use of 2,2'-(1-methyl-1,2-ethanediylidene)bis[hydrazine carboximidamide] according to any of claims 7 and 8 for the preparation of a pharmaceutical composition intended to treat cancer or malignant diseases.